Corrugated balloon flue

ABSTRACT

A plurality of standardized flue sections or modules of double wall construction are assembled together to form a complete flue assembly for hot smelter gases. Each flue section comprises a pair of generally annular end flanges spaced a predetermined standard distance apart, an inner wall of corrugated corrosion resistant sheet metal extending between and secured to the facing surfaces of the two end flanges, an outer wall of corrugated sheet metal also secured to the end flanges and spaced a predetermined distance radially outwardly of the corrugated inner wall, and means for connecting the end flanges of one flue section to the abutting end flanges of adjoining flue sections.

Unlted States Patent [1 1 [111 3,740,930 Cullom June 26, 1973 CORRUGATED BALLOON FLUE 3,445,101 5/1969 Reighart 266/16 r 3,363,591 1 1968 L 11 I84 [761 lnvenm" J 1 1 23 1 Avenue 3,368,506 2/1968 118/184 San Manuel, Ariz. 85631 [22] Filed: Apr. 28, 1971 Primary Examiner-Bernard Nozick n No: 138,252 figtzzzy-Penme, Edmonds, Morton, Taylor and [52] US. Cl. 55/269, 98/60, 110/119, 57 ABSTRACT 5 l I 1 2/ 138/114 138/148 2 A plurality of standardized flue sections or modules of l d l l 4 155 double wall construction are assembled together to l 1 7 l form a complete flue assembly for hot smelter gases. 1 l 184 15 31 3 Each flue section comprises a pair of generally annular l /l30 2 end flanges spaced a predetermined standard distance apart, an inner wall of corrugated corrosion resistant 5 6 R t d sheet metal extending between and secured to the fac- 1 m ing surfaces of the two end flanges, an outer wall of cor- UNITED STATES PATENTS rugated sheet metal also secured to the end flanges and 1,045,459 11/1912 Todd et a1. /184 spaced a predetermined distance radially outwardly of 1,130,596 3/1915 the corrugated inner wall, and means for connecting the end flanges of one flue section to the abutting end 3 5 1967 flanges of ad ornlng flue sections. 3,332,446 7/1967 Mann 138/148 8 Claims, 4 Drawing Figures PAIENIEUJIINZ 97 3.740.936

/ 2 BY; fl

ATTORNEYS CORRUGATED BALLOON FLUE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to flues for hot smelter gases, and more particularly to an improved balloon flue assembly for the very hot and corrosive flue gases from a copper smelter.

2. Prior Art Pyrometallurgical processes such, for example, as the smelting and converting operations at a conventional copper smelter produce large quantities of extremely hot and, usually, corrosive flue gases. These flue gases are usually treated to recover the heat content thereof and to remove dust and sulfur dioxide therefrom before being discharged to the atmosphere, the gases being conveyed from the furnace or converter in which they are generated to the subsequent operations by means of suitable flues. When the volume and temperature of the flue gases being generated remain fairly uniform, the problem of constructing a flue capable of handling these flue gases is relatively free of complications. However, when the volume and temperature of the flue gases vary widely over a period of time as in the case of the sulfurous flue gases produced by a copper converter, many problems are encountered in the design and maintenance of flues for such flue gases which are attributable to the extremes in temperatures and to the corrosive character of the gases.

Flues for converter flue gases are normally constructed of heavy gauge sheet steel or steel plate supported by sturdy metal frame work which, in turn, is provided with a sheet metal cover or roof which protects the flue proper from the elements and prevents dirt and other foreign objects from falling on and possibly damaging the flue. These steel flues which are commonly called balloon flues because of the balloon-like configuration of their transverse cross section lead from the uptake of each converter to a common main flue and thence to the subsequent operations for the removal of dust and sulfur dioxide therefrom. The temperature of the flue gases generated by a converter varies widely with the cyclic activities of the converter, dropping at times below the dew point of sulfurous acid which results in severe corrosion of the carbon steel shell of the flue, and at other times rising to above the working temperature of carbon steel to red heat which results in warping and tearing of the metal from expansion and contraction.

Experience has shown that a balloon flue for converter gases of conventional construction installed at a major copper smelter usually begins to fail within about a year of its construction. After an extensive investigation of the cause of the failure of conventional flues I have determined thatthese problems are caused by uneven linear expansion, leaking thermal expansion joints, localized expansion, corrosion from heat, corrosion from acid at temperatures below the dew point, and the need for protection of the flue from weather and other external foreign objects. In particular, I found that one of the most important components of the problem is the abrupt and extensive variation in the temperature of the flues in various areas resulting in local hot spots which buckles the metal and causes it to tear. The openings thus formed allow cold air to enter the flue with the resulting condensations of acid vapors and consequent destructive corrosion of the flue. An-

other important component of the problem is the uneven linear expansion of the flue. Expansion joints are provided at intervals to accommodate linear expansion. However, because movement of the flue under heat is somewhat capricious, some joints are crowded and damaged while little or no movement takes place at other joints. In addition expansion joints ordinarily leak air and the cold air causes acid condensation which damages the flue at the joints.

After an extensive investigation I have devised an improved balloon flue assembly for hot smelter gases which overcomes the problems herein before described. The flue of the invention is characterized by a modular double wall construction of light weight corrugated sheet metal. The resulting flue structure is gas tight and devoid of troublesome expansion joints, extremely light in weight, and highly resistant to the deleterious effects of hot, corrosive flue gases.

SUMMARY OF THE INVENTION The improvement in balloon flues for hot smelter gases, and in particular for converter gases, comprises a plurality of standardized flue sections of modular double wall construction which are assembled together to form a complete flue assembly. The flue may have a circular or an oblong or, in particular, a balloonshaped transverse cross section, and most flue assemblies include a combination of such flue cross sections. In accordance with the invention each flue section comprises a pair of generally annular end flanges which are spaced a predetermined standard distance apart, the inner periphery of each flange conforming generally to the periphery of the transverse cross section of the flue. An inner wall of corrugated corrosion resistant sheet metal extends between and is secured to the facing surfaces of the two end flanges adjacent the inner periphery thereof. An outer wall of corrugated sheet metal also extends between and is secured to the facing surfaces of the two end flanges. The corrugated outer wall is spaced a predetermined distance radially outwardly with respect to the corrugated inner wall, the inner and outer walls thus defining an annular space that extends from one end flange to the other end flange of the flue section. The standardized flue sections are designed to be assembled together with the end flanges of one flue section abutting the end flanges of adjoining flue sections to form a flue assembly of the desired length, and consequently means are provided for connecting the end flanges of one flue section to the abutting end flanges of the adjoining flue sections.

Each flue section is advantageously provided with means for collecting and removing the dust that settles out of the hot smelter gases passing through the flue. The means for collecting the dust advantageously comprises a U-shaped longitudinal trough disposed at the lowest point of the flue cross section defined by the inner wall of the flue section; and the means for removing the dust advantageously comprises a screw conveyor disposed in the trough which conveys the dust longitudinally to a dust discharge opening. In an advantageous embodiment of the invention the flue section has a balloon-shaped configuration in which case the lowermost longitudinal edges of the inner wall of the flue section are connected to the longitudinal dust collector trough which forms the bottom closure of the flue gas conduit defined by the inner wall of the flue section. The lowermost longitudinal edges of the outer wall of the flue section terminate radially outwardly with respect to the bottom closure of the inner wall so that the annular space between the inner and outer walls is open to the atmosphere adjacent the lower longitudinal edges of the outer wall. Adjustable vent means for the annular space between the inner and outer walls are advantageously disposed at the uppermost point on the outer wall of the flue section so that the upward flow of air in the annular space can be controlled or prevented.

The corrugated sheet metal of the inner and outer walls is positioned with respect to the longitudinal axis of the flue section so that the undulations of the sheet metal proceed longitudinally from one end flange to the other. The corrugated inner wall must be resistant to both heat and corrosion, and advantageously is formed of heat stabilized stainless steel sheet. The corrugated outer wall of the flue section is not exposed to such high temperatures or to such corrosive gases as the inner wall, and therefore the outer wall is advantageously fabricated from ordinary stainless steel sheet or aluminum sheet metal. The corrugations and the heat and corrosion resistant properties of the inner and outer walls of the flue section largely prevent the rending and corrosion which has been the cause of the rapid destruction of prior converter flues. Moreover, the double wall construction of the flue section and the provision of means for cooling or insulating the inner wall thereof materially contributes to the strength, light weight and durability of the converter flue assembly.

BRIEF DESCRIPTION OF THE DRAWING The improved flue assembly of the invention will be better understood from the following description thereof in conjunction with the accompanying drawings of which FIG. 1 is a plan view of a flue assembly embodying the standardized flue sections of the invention,

FIG. 2 is a side elevation partly broken away of a flue section before being assembled together with other similar flue sections,

FIG. 3 is an enlarged sectional view along line 33 of FIG. 1 showing the manner of mounting the flue section, and

FIG. 4 is a much enlarged sectional view along line 44 of FIG. 1 showing one manner in which end flanges of two flue sections may be joined together.

DESCRIPTION OF PREFERRED EMBODIMENT verter (not shown) and the other end thereof is connected to the main flue portion 12, and one end 16 of the discharge flue portion 13 is connected to the main flue portion 12 and the other end 17 thereof communicates with process equipment (not shown) for the removal of dust and sulfur dioxide from the flue gases prior to discharge to the atmosphere. The converter flue portions 11, the main flue portion 12 and the discharge flue portion 13 may have a circular or an oblong or, in particular, a balloon-shaped transverse cross section (such as that shown in FIG. 3), or the flue portions may be a combination of such flue cross sections. In accordance with the invention, however, the flue portions 11, 12 and 13 of the flue assembly each comprise a plurality of modular flue sections 18 of generally standardized size and construction so that, in-so-far as possible, the flue sections 18 are interchangeable and are readily replaceable by other modular flue sections of the same standard size. Although the length and cross sectional configuration of the flue sections 18 of one portion (for example the converter flue portion 1 1) may differ from the flue sections 18 of other portions (for example, the main flue portion 12) of the flue assembly, and although special purpose flue sections 19 and 20 must be provided at the junctions of the converter flue portions and the discharge flue portion with the main flue portion, all of these flue sections share the modular double walled construction which characterizes the flue structure of the invention as hereinafter described.

As shown in FIGS. 2, 3 and 4, each flue section 18 comprises a pair of generally annular end flanges 21 and 22 which are spaced a predetermined standard distance apart (say, 10 or 12 feet apart). The inner periphery of each end flange 21 and 22 conforms generally to the periphery of the transverse cross section of the flue which, as previously noted, may have a circular, oblong or balloon-shaped configuration. An inner wall 23 of corrugated corrosion resistant sheet metal extends between and is secured to the facing surfaces 21a and 22a of the end flanges 21 and 22 adjacent the inner periphery thereof, the corrugated inner wall 23 comprising the flue gas conduit of the flue section. An outer wall 24 of corrugated sheet metal also extends between and is secured to the facing surfaces 21a and 22a of the two end flanges, the corrugated outer wall 24 being spaced a predetermined distance (the distance d in FIG. 4) radially outwardly with respect to the corrugated inner wall 23 of the flue section so that the corrugated inner and outer walls 23 and 24 define an annular space 25 that extends from one end flange 21 to the other end flange 22 of each flue section 18. In all cases the corrugated sheet metal from which the inner and outer walls 23 and 24 are fabricated is aligned or positioned so that the undulations of the sheet metal proceed longitudinally from one end flange to the other, as clearly shown in the drawings.

In the embodiment of the flue shown in the drawings, the upper portion of the flue section 18 has a semicylindrical configuration and the lower portion of the flue section has a truncated V-shaped configuration so that the overall transverse cross section of the flue section 18 has a balloon-shaped configuration (as shown best in FIG. 3). The lowermost longitudinal edges of the inner wall 23 are not directly connected to each other but instead are connected to a longitudinal dust collecting trough 26 which forms the bottom closure of the flue gas conduit defined by the inner wall of the flue section. The dust collecting trough 26 advantageously has a U-shaped transverse cross section which is adapted to receive means (for example, the screw conveyer 27) for conveying dust which collects in the trough 26 to a dust discharge opening formed therein. The lower ends of the generally annular end flanges 21 and 22 terminate above the dust collecting trough 26 as shown in FIG. 3 in order to accommodate the trough 26. In addition, the lower longitudinal edges of the outer wall 24 of the flue section 18 terminate above and radially outwardly with respect to the dust collecting trough 26 so that the annular space 25 between the inner and outer walls 23 and 24 of the flue section is open to the atmosphere along the lower longitudinal edges of the outer wall thereof. Adjustable vent means 28 which may be opened or closed at will are advantageously located adjacent the uppermost point of the outer wall 24, the vent means communicating with the interior annular space 25.

The generally annular end flanges 21 and 22 of each flue section 18 serve to support the corrugated inner and outer walls 23 and 24 and are adapted to be connected to the abutting end flanges of adjoining flue sections 18. These end flanges must be strong and rigid and, because of their location in the flue structure, are not subject to serious corrosion. Accordingly, I presently prefer to fabricate the end flanges of mild steel plate. In the embodiment shown in FIG. 4 of the drawing the end flanges 21 and 22 are each provided with a channel shaped member 30 which is secured by welding or the like to the vertically disposed surface thereof. The corrugated inner wall 23 is secured to the inner wall of the channel member 30 by means of a plurality of circumferentially spaced bolts or other fastening members 33, and the corrugated outer wall 24 is secured to the outer wall of the channel member 30 by means of a plurality circumferentially spaced bolts or other fastening members 34. As noted, the inner and outer walls 23 and 24 are radially spaced apart a predetermined distance d that is maintained at the end flanges 21 and 22 by the channels 30 and between the end flangesby the spacer members 31. Means are provided for securing the abutting end flanges 21 and 22 of adjoining flue sections together, the means for joining the end flanges advantageously (but not necessarily) comprising a plurality of circumferentially spaced bolts 35 which extend through matching holes formed in the abutting end flanges 21 and 22. The flue sections thus assembled together to form the flue assembly are supported by a suitable frame work of light weight steel beams 36 and brackets 37 which are advantageously positioned at each end of the assembled flue sections.

As noted, the inner wall 23 serves as the actual flue gas conduit for the flue gases flowing through the flue assembly and, as such, is directly exposed to the extremes in temperature and to the corrosive properties that are characteristic of, say, converter flue gases. Accordingly, the corrugated inner wall 23 must be fabricated from a corrosion resistant material which is capable of withstanding the extremes in temperature and the corrosive gases to which it is exposed in service, and l presently prefer to use heat stabilized stainless steel (for example type 321, 347 or 348 stainless steel) for the inner wall 23. The corrugated outer wall 24 serves to protect the inner wall 23 from the elements and from foreign objects as well as to define the outer wall of the annular space 25. The outer wall 24 is not directly exposed to such extremes in temperature or to such highly corrosive gases as is the inner wall 23. Accordingly, the outer wall 24 is advantageously fabricated from less expensive corrugated sheet materials which nonetheless possesses corrosion resistant characteristics, and I presently prefer to use type 301 or 302 stainless steel or aluminum alloys for this purpose.

As previously described, the inner wall 23 of the flue comprises the actual gas conduit through which the hot and corrosive flue gases flow, and therefore it 18 exposed to the extremes in temperature and to the effects of corrosive gases which have proved to be so destructive of prior converter flues. The corrugations and the corrosion resistant properties of the sheet metal from which the inner wall 23 is fabricated largely prevent the rapid deterioriation of the flue heretofore experienced. It is nonetheless desirable to provide means for cooling the inner wall 23 at those areas where it is exposed to excessive high temperatures and to insulate the inner wall against loss of heat in other areas to prevent condensation of acid vapors in the flue gas at those other areas. As previously noted, the outer wall 24 is spaced radially outwardly with respect to the inner wall 23 to define the annular space 25 therebetween. The annular space 25 advantageously communicates with the atmosphere along its open lowermost longitudinal edge, and it advantageously also communicates with the atmosphere at its uppermost portion by means of the adjustable vent 28. When the adjustable vent 28 is open, air flows upwardly through the annular space 25, thereby serving to cool the inner wall 23 of the flue. When the vent 28 is closed, stagnant air retained in the annular space 25 serves as insulation for the inner wall 23 to prevent loss of heat and consequent condensation of acid vapors in the flue gases flowing through the flue assembly.

The unique modular flue sections of corrugated, double wall construction herein described provide a light weight gas tight flue assembly that requires no trouble prone expansion joints to accommodate the extremes in temperatures encountered in normal service. The flue assembly is essentially immune to attack by the hot corrosive gases contained in the flue not only because of the corrosion resistant properties of the sheet mate rials from which it is made but also because of the measures provided for preventing the leakage of cold air into the flue and for the insulation of the flue to prevent heat losses therefrom.

I claim:

1. A balloon flue for hot smelter gases which comprises a plurality of standardized flue sections assembled together to form the complete flue assembly, each flue section comprising a pair of generally annular end flanges for said flue section spaced a predetermined standard distance apart, the inner periphery of each flange conforming generally to the periphery of the transverse cross section of the flue,

a perimetric inner wall of substantially parallel and transversely corrugated corrosion resistant sheet metal extending between and secured to the facing surfaces of the two end flanges adjacent the inner periphery thereof, said corrugated inner wall defining the gas-tight flue gas conduit of the flue section,

a perimetric outer wall of substantially parallel and transversely corrugated sheet metal extending between and secured to the facing surfaces of the two end flanges, said corrugated outer wall being spaced a predetermined distance radially outwardly of the corrugated inner wall of said flue section so that said spaced inner and outer walls define an annular space that extends from one end flange to the other end flange of said flue section, the lowermost portion of said corrugated outer wall being formed with an opening so that said annular space is open to the atmosphere thereat, and

means for connecting the end flanges of one flue section to the abutting end flanges of adjoining flue sections.

2. The flue assembly according to claim 1 in which each flue section is provided with means for collecting and removing the dust that settles out of the hot smelter gases passing through the flue.

3. The flue assembly according to claim 2 in which the means for collecting and removing the dust comprises a U-shaped longitudinal trough disposed at the lowest point of the flue cross section defined by the inner wall of the flue section, dust conveyor means being disposed in said trough for conveying the dust collected therein to a dust discharge means.

4. The flue assembly according to claim 1 in which the outer wall of at least one of the flue sections is provided with vent means that communicates with the interior of the annular space between the inner and outer walls of the flue section, said vent means being disposed adjacent the uppermost point of said outer wall and being adjustable to control the flow of air through said vent.

5. The flue assembly according to claim 1 in which the upper portion of at least one of the flue sections has a semi-cylindrical configuration and the lower portion of said flue section has a truncated V-shaped configuration so that the transverse cross section of said flue section has a balloon-shaped configuration, the lowermost longitudinal edges of the inner wall of the flue section being connected to a longitudinal dust-collecting trough which forms the closure for the bottom of the inner wall of said flue section, and the lowermost longitudinal edges of the outer wall of said balloon flue section terminating radially outwardly of said bottom closure of the inner wall of the flue section so that the annular space between the inner and outer walls of the flue section is open to the atmosphere adjacent the lower longitudinal edges of the outer wall thereof.

6. The balloon flue according to claim 5 in which said flue section is provided with adjustable vent means disposed on the outer wall of said flue section adjacent the uppermost point thereof.

7. The flue assembly according to claim 1 in which the corrugated inner wall is formed of heat stabilized stainless steel.

8. The flue assembly according to claim 1 in which the corrugated outer wall is formed of stainless steel or aluminum. 

1. A balloon flue for hot smelter gases which comprises a plurality of standardized flue sections assembled together to form the complete flue assembly, each flue section comprising a pair of generally annular end flanges for said flue section spaced a predetermined standard distance apart, the inner periphery of each flange conforming generally to the periphery of the transverse cross section of the flue, a perimetric inner wall of substantially parallel and transversely corrugated corrosion resistant sheet metal extending between and secured to the facing surfaces of the two end flanges adjacent the inner periphery thereof, said corrugated inner wall defining the gas-tight flue gas conduit of the flue section, a perimetric outer wall of substantially parallel and transversely corrugated sheet metal extending between and secured to the facing surfaces of the two end flanges, said corrugated outer wall being spaced a predetermined distance radially outwardly of the corrugated inner wall of said flue section so that said spaced inner and outer walls define an annular space that extends from one end flange to the other end flange of said flue section, the lowermost portion of said corrugated outer wall being formed with an opening so that said annular space is open to the atmosphere thereat, and means for connecting the end flanges of one flue section to the abutting end flanges of adjoining flue sections.
 2. The flue assembly according to claim 1 in which each flue section is provided with means for collecting and removing the dust that settles out of the hot smelter gases passing through the flue.
 3. The flue assembly according to claim 2 in which the means for collecting and removing the dust comprises a U-shaped longitudinal trough disposed at the lowest point of the flue cross section defined by the inner wall of the flue section, dust conveyor means being disposed in said trough for conveying the dust collected therein to a dust discharge means.
 4. The flue assembly according to claim 1 in which the outer wall of at least one of the flue sections is provided with vent means that communicates with the interior of the annular space between the inner and outer walls of the flue section, said vent means being disposed adjacent the uppermost point of said outer wall and being adjustable to control the flow of air through said vent.
 5. The flue assembly according to claim 1 in which the upper portion of at least one of the flue sections has a semi-cylindrical configuration and the lower portion of said flue section has a truncated V-shaped configuration so that the transverse cross section of said flue section has a balloon-shaped configuration, the lowermost longitudinal edges of the inner wall of the flue section being connected to a longitudinal dust-collecting trough which forms the closure for the bottom of the inner wall of said flue section, and the lowermost longitudinal edges of the outer wall of said balloon flue section terminating radially outwardly of said bottom closure of the inner wall of the flue section so that the annular space between the inner and outer walls of the flue Section is open to the atmosphere adjacent the lower longitudinal edges of the outer wall thereof.
 6. The balloon flue according to claim 5 in which said flue section is provided with adjustable vent means disposed on the outer wall of said flue section adjacent the uppermost point thereof.
 7. The flue assembly according to claim 1 in which the corrugated inner wall is formed of heat stabilized stainless steel.
 8. The flue assembly according to claim 1 in which the corrugated outer wall is formed of stainless steel or aluminum. 